1. Field of the Invention
The present invention relates generally to apparatuses and methods for adjusting brightness and contrast of electronic displays, and especially to an apparatus and method for adjusting brightness and contrast in a display device by operating a single key.
2. Description of the Related Art
A display is a very important part of a typical image output apparatus. Various kinds of displays include CRT (Cathode-Ray Tube) displays, LCDs (Liquid Crystal Displays), and PDPs (Plasma Display Panels). In typical LCDs, the display function is supported by a back light. The brightness of the back light determines the brightness of images shown on the display. The contrast of an image means the degree of difference between the light and dark parts of the image. In theory, the higher the brightness of the display, the better the image is; and if the contrast is one hundred percent, the display can clearly provide an abundance of different colors. Accordingly, adjustment of brightness and contrast has a tremendous impact on the quality of the image.
Modern displays generally provide for separate adjustment of brightness and contrast. However, some displays provide adjusting of brightness and contrast via a single knob. For example, in the TDS-7xxD series oscilloscopes manufactured by Tektronix Inc, the contrast and brightness functions are controlled via a single knob, which is assigned to each function by means of a menu-prompted choice. From the user's point of view, control of these functions is essentially the same as having two knobs, one for brightness and one for contrast. The single knob does not provide simultaneous adjusting of both contrast and brightness in a single operation.
The art of adjusting brightness and contrast in a monitor is disclosed in publications such as U.S. Pat. No. 6,239,782 entitled “Single Knob Intensity Control For Use In Digital Test And Measurement Equipment” and issued on Mar. 29, 2001. This patent provides an apparatus and method used in a test and measurement instrument for simultaneously adjusting both contrast and brightness via a single knob. The method employs a family of modified gamma curves each having multiple breakpoints for mapping multiple-byte pixel intensity words into a multi-bit pixel intensity display control word. A single user-operable intensity control accomplishes selection of a particular gamma curve from the family of gamma curves, and actuates the simultaneous adjustment of both contrast and brightness.
However, the apparatus described in the patent requires that the pixel intensity values of the curves be stored in the memory of the apparatus in advance. In addition, the apparatus needs to compare the brightness value obtained from the single knob with inputted pixel intensity values. This greatly increases the burden placed on the operating hardware, and makes the apparatus difficult to operate.
What is needed is an apparatus and method for simultaneously adjusting brightness and contrast which can overcome the above-described problems.